Edward a



UNrrED sTATEs 'PATENT oFFIoE.

EDWARD A. L. ROBERTS, OF NEW YORK, N. Y.

FURNACE FOR DENTAL PURPOSES.

Specification of Letters Patent No. 24,823, dated July 19 1859.

T o all rwhom it may concern.'

Be it known that I, EDWARD A. L. Ro- ER'rs, of the city and State of New York, have invented and devised a new and Improved and Useful Furnace for Dental Purposes, Oapeling Metals, and for other Uses;

and I do hereby declare that the following y is a full, clear, and exact description thereof, and of its construction and mode or manner of operation, reference being had to the accompanying drawings, and to the letters of reference marked thereon, making a part of this specification.

Figure l, is a perspective view. Fig. 2, is a like view of a smaller furnace. Fig. 3, is a section above the grates. Fig. 4, is a vertical section of Fig. 3. Fig. 5, is a section of a muflle.

The character and object of my invention consists in constructing a furnace, which is compact in form, not expensive, silnple in operation, and which gives and secures an intense heat with little fuel, and in a much less time than can be obtained in ordinary furnaces.

The base of the furnace A, is of cast iron, or any other suitable material, in which are two sets of grates c, c, Figs. 3, 4, each hung on axles at the upper corners, and inclining downward and toward the center at angles of about degrees, and resting at the center upon the bar cZ,-which may be curved,

as shown by the line of the grates in Fig. 3,

so as to secure better support-when in use, but which swing down, as shown by the dotted lines in Fig. 4, when the bar d, is turned, to drop the fire, and for cleaning &c. The draft doors a, a, slide so that the amount of air or draft may be regulated at pleasure; they also give access for the removal of ashes &c. Similar doors may also be placed on the opposite side of the furnace.

The upper part B, of the furnace is constructed of baked fire clay or bricks, molded in the form required for the several sides and top, each of which is generally a single piece in the smaller furnaces, and all of which are strapped by suitable binders of iron. Openings D, Fig. l, and F, Fig. 3, are left for supplying coaland similar openings may be made in the other sides or top of the furnacemand are closed with a suitable fire brick plug. Other openings C, C,

are for receiving mufiles O, for holding teeth, or any other matter to be heated, or for inserting retorts of any kind. The u-pper part B, of the furnace is in form a truncated pyramid, by means of which the draft is increased, as the greatest area is at the bottom, thus exposing the largest surface to the action of the draft; this form also causes the heat to radiate toward the center, where or at about which, the muflies, retorts &c. will naturally be placed.

The muflies C are generally made in the form of a triangular prism with rounded angles, and having the lower corners b thicker than the sides or bottom, whereby the liability of cracking is almost entirely prevented. Through the top 0f such lnuiie is also an opening b, Fig. 5, to allow the gases to pass off freely, which otherwise would be absorbed in the inutile, and tend to discolor the work. These inutiles, when it is desired to retain the heat in them, are also closed by lire brick plugs, in the same manner as the openings D, F.

Then the furnace is used for capeling or treating metals, the muilles or their equivalents will connect, or open into, at their back ends, iues, in the furnaces connecting with the main flue, and the mouth of the muilie will be left open to allow the free entrance of atmospheric air necessary for such operations.

As before stated, the grates c, c, are inclined inward and downward, from which several advantages are derived. It secures a greater surface of grate in a given space; and it causes the greatest heat to be at the place where most needed, that is, at or about the center, the two grates being in fact two fires inclined toward each other, and acting, as do also the sides of the part B, as reflecting surfaces, and increasing the intensity of the heat at and toward the center, near or above which the muflles, retorts &c. will naturally be placed. The inclined position of the grates, and the inclination of the sides of the furnace, makes also the lire self supplying, or makes the upper coal, from the combustion of that below, naturally drop down toward the center, and causes the coal continually to slide under the muffles, retorts Sec.; and such movement of the coal also tends to clear the grate of ashes and other matter, which produce cinders, and from which great trouble is experienced in all common furnaces, Where intense heat is necessary. Indeed, in my furnace no trouble is experienced from slag, cinders &c., and a free, clear re is always maintainable. By its use it is also found that a like degree of heat can be obtained in fifteen minutes as can be obtained in ordinary urnaces in from twenty five to thirty minutes. This furnace can also be used and With much advantage in enameling and like Y uses. -It' can also be made of small size suitable for limited experiments or operations, and With as good effect as more costly and extensive ordinary furnaces.

E. A. L. ROBERTS.

Vitnesses:

S. D. LAW, W. J. DEMoREsT. 

